It is known to have different operators providing wireless mobile service to subscribers with overlapping coverage. There are a number of ways for operators to invest in spectrum and infrastructure to provide more capacity or more coverage. An operator can for example:                Invest in spectrum & infrastructure;        Invest in spectrum & share infrastructure CAPEX with another operator;        Share CAPEX in spectrum & infrastructure with another operator;        Operate as a Virtual Mobile Network Operator, i.e. lease spectrum from one of the above.        
It is known to share resources between operators, as shown in US2014023016, which explains that one network sharing configuration which may be considered is the so called Multi-Operator Random Access Network (MORAN) configuration where operators share the physical network equipment but do not share the spectrum, i.e. each operator uses different carriers. The advantage with the MORAN configuration is that each operator has full control over the configuration of broadcast parameters used in their spectrum, giving more freedom to have operator specific configurations. The drawback however is that the operators are not able to benefit from spectrum sharing leading to lower utilization of radio resource and lower network capacity. US2014023016 proposes a way of overcoming this restriction and sharing carriers in a MORAN configuration by using carrier aggregation, and by sending a resource configuration message to a UE to enable it to configure another carrier as a secondary component carrier.
It is also known to provide spectrum sharing within the same carrier, as well as sharing network infrastructure and sites. This can reduce the total deployment costs, and may further provide benefits due to pooling of the available spectrum. A drawback is that it requires significant cooperation between the operators sharing the network since the network configuration is common for the part of the network that is shared, making it difficult to differentiate the treatment of users from each operator. This also makes interaction, e.g. handover, between shared parts and non-shared parts more complex, since the shared part needs to interact with a multiple of non-shared networks.
Support for such network sharing has recently been enhanced in the third Generation Partnership Project (3GPP) Universal Terrestrial Radio Access Network (UTRAN) and Evolved-UTRAN standards. The standards allow various scenarios for network sharing, but it is expected that a common scenario will be when the Radio Access Network (RAN) is shared and each operator has its own Core Network (CN). This scenario is called Multi-Operator Core Network (MOCN) in 3GPP. From a technical point of view the MOCN configuration uses the multi-to-multi connectivity of the interfaces between the Radio Network Controller (RNC) and CN, and the evolved Node B (eNB) and the CN, respectively. This makes it possible to connect a Radio Access Network (RAN) node, e.g. RNC or eNB, to multiple CN nodes, e.g. Serving General Packet Radio Service Support Node and Mobile Management Entity (MME), belonging to different operators. The RAN will in this configuration broadcast one Public Land Mobile Network (PLMN) identity for each operator sharing the RAN. The UE will at initial attach select which PLMN it wants to connect to and the RAN will make sure that the initial attach signalling is routed to the correct operators CN. Once the UE has been assigned a CN node there are also mechanisms making it possible for the RAN and CN to route subsequent signalling related to this UE to the same CN node. Besides the list of PLMN IDs, most system information broadcasted on the cell broadcast channels in the shared RAN is common for all operators sharing the RAN. Capacity boost cells (also called small cells) can be added by each operator to increase capacity, using the same carrier. A UE subscribing to one operator checks the system information broadcast from the cell to see if it belongs to the same operator and is therefore available to connect to.
With ever increasing capacity demands there continues to be a growing variation between peak demand and outside busy hour needs. However, operators are forced to dimension for peak demands, resulting in poor use of network resources (spectrum & infrastructure) during off-peak times. As operators focus on different service offerings targeting different business segments, one operator's needs (spectrum & infrastructure) at different times and locations may vary greatly from another and this variation will continue to grow as networks evolve towards 5G. None of the above deployment scenarios enable an operator to optimize their ROI in this situation.